linux-kernel - Re: [PATCH v2] bpf: BPF based latency tracing

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Date:	Mon, 22 Jun 2015 09:34:18 +0200
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Daniel Borkmann <daniel@...earbox.net>,
	Alexei Starovoitov <ast@...mgrid.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v2] bpf: BPF based latency tracing

On 06/20/2015 10:14 AM, Daniel Borkmann wrote:
> I think it would be useful to perhaps have two options:
> 
> 1) User specifies a specific CPU and gets one such an output above.

Good point. Will do.

> 2) Summary view, i.e. to have the samples of each CPU for comparison
>    next to each other in columns and maybe the histogram view a bit
>    more compressed (perhaps summary of all CPUs).

I agree, the current view is not really optimal. I'll look into this as
well.

Alexei indicated that he is working on per-cpu variables support. I
think that would be extremely useful to drop the hard coded limit of
CPUs and turning this sample code into some more generic code.

> Anyway, it's sample code people can go with and modify individually.

I am interested to turn this code into a more useful tool. Though I
think I miss some background information why this code is kept as
samples. Obviously, there is the API and ARCH dependency. As long as an
API change can reliable be detected I don't see a real show stopper.
Maybe I am too naive. Furthermore I expected that trace_preempt_[on|off]
wont change that often.

> Acked-by: Daniel Borkmann <daniel@...earbox.net>

Thanks,
Daniel
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